In the sport of alpine skiing, performance is often a measure of the skier's ability to maintain precisely carved turns. Carved turns track a smooth and continuous path that is at all times parallel to that portion of the ski located beneath the ski boot. The alternative to a precisely carved turn is a skidded turn. Skidding occurs when the skier rotates, points or directs the skitoward the inside of the direction the skier is actually travelling. When this occurs the ski is no longer tracking along its length but is skidding sideways. This sideways skidding of the ski results in a loss of speed. For this reason, precise carving of turn is critical to achieve good results in the sport of alpine ski racing. Precisely carved turns enable the skier to maintain the fastest line or path through a race course. Additionally, a carved turn prevents the skier from being forced to deal with erratic lateral motions and forces that are created once a ski begins to skid sideways.
When referring to alpine ski construction, “sidecut” refers to the narrowing of the waist of the ski, near the mid length of the ski. In the early days of alpine ski racing, skis possessed a very slight or minimal sidecut. However, in the 1980s ski designers began to understand that increased sidecut allowed more precise ability to carve the ski; the slightly wider tip and tail of the ski combine with the narrow mid-section waist to form an hourglass shape to the ski. This hourglass shape allows the ski to de-camber (i.e., bend into an arc) when the ski is placed on edge and turning forces are applied. Throughout the early era of alpine ski racing, the most successful competitors were those able to bend or de-camber the skis into an arc that precisely matched the radius of curvature of the path the skier hoped to travel. By bending the ski into to this arc and maintaining the ski on edge, accomplished ski racers travelled a precisely carved arc with minimal or no lateral skidding. Just as importantly, by carving precise turns with the skis de-cambered the skier is actually able to laterally accelerate the ski in the turn. In contrast, when a skier is unable to de-camber a ski in a turn and the ski skids sideways, the speed of the skier decreases and control is decreased due to diminishment in the performance characteristics of the ski. Clearly, in the sport of alpine ski racing, speed and control are of utmost importance and therefore, skidded turns are undesirable.
The sport of alpine skiing experienced a revolution with the introduction of the shaped ski. Shaped skis have considerably increased sidecut. This is accomplished by increasing the width of the ski at the tip and tail while reducing or maintaining a narrow ski width at the waist. The shaped ski provides a sidecut that forms a reduced radius of curvature versus traditional alpine skis. This development allowed skiers of many ability levels to begin to experience precisely carved turns, even without appreciably de-cambering the skis. Simply by rolling or placing the skis over onto the edges, the average skier began to experience the stability and precision of a carved turn, free from lateral skidding.
By softening or reducing the flexural stiffness of alpine skis, skiers of moderate or average ability began to experience carved turns as they learned to bend the skis into arcs rivaling those of professional ski racers. The increased sidecut of the shaped ski allowed flexurally softer skis to de-camber and form tighter radius turns as moderate to advanced skiers learned to place the ski on edge and load it with turning forces. The shaped ski revolution brought increased lateral acceleration (associated with tighter radius turns) and precise tracking of the turns along the ski's length, free of lateral skidding, to the masses of the skiing public. The narrow-waisted, wide-in-tip-and tail shaped skis, in combination with reduced flexural stiffness transformed the sport of alpine skiing allowing skiers of even moderate ability to experience the acceleration and stability of the precisely carved turn.
One drawback of this technological revolution involves a balance between the ski's torsional rigidity versus flexural stiffness. Flexural stiffness is a measure of the force required to bend the ski upward (at the tip or tail) some given distance along the longitudinal axis defined by the ski. On the other hand, torsional rigidity is a measure of the amount of torque required to twist or warp the ski some given angular rotation about the ski's longitudinal axis. The softer flex and increased sidecut of modern skis effectively reduce the torsional rigidity of the ski. Reduced torsional rigidity allows the ski to twist about its longitudinal axis as the skier places the ski on edge and loads it into the turn. This twisting of the ski effectively reduces the amount of edge angle at the ski tip (or tail) versus the amount of edge angle at the ski mid-length (beneath the ski boot sole). Depending upon snow conditions, the edge angle, that is, the amount that the ski is rotated about the long axis relative to the surface of the snow, may determine whether a ski continues to carve along its length versus breaking loose into a lateral skid. For this reason, torsional rigidity is a very important and desirable characteristic for a high performance ski.
Unfortunately, both the increased sidecut and softer flexural characteristics of modern shaped skis compromise or reduce torsional rigidity. Ski manufacturers strive to reduce this inherent trade-off by employing advanced materials and creative composite lay-up techniques. Nonetheless, softer flexing skis with increased sidecut offer inherently reduced torsional rigidity. Reduced edge angles at the tip and tail resulting from this lesser torsional rigidity compromise the ski's ability to hold an arc when highest levels of performance are called for.
There is a need therefore for shaped skis that have soft flexural characteristics while maintaining torsional rigidity.
Freely flexing torsional stiffener techniques as described within this specification eliminate the tradeoffs between softer flex and increased sidecut versus torsional rigidity. The technologies, techniques and methods described within this specification enable a very soft flexing ski to exhibit near perfect torsional rigidity. Perfectly rigid torsion would be a ski that encounters no twisting about its length, regardless of the turning forces exerted in the ski. These innovations allow modern skis to deliver almost constant edge angle throughout the length of the ski, from boot-sole region to the tip and from boot-sole region to the tail. These advances deliver a new level of ultimate performance to the modem, easy carving soft flexing and increased sidecut skis, as well as skis for more advanced skiers and even skis build specifically for the performance required during racing.
The torsional stiffener of the present invention comprises apparatus for increasing the torsional rigidity of skis without influencing the ski's flexural characteristics. There are numerous embodiments of the invention disclosed for preventing torsional rotation of a ski about its longitudinal axis while at the same time having little to no impact on the flexing characteristics of the ski. The innovations defined by the invention may be delivered through exoskeletal means (via mechanisms and linkages attached directly to snow skis) or through dynamic structural members or mechanisms integrated within the ski design itself. In all cases, these techniques effectively reduce the ski's tendency or proclivity to twist about its longitudinal axis when subjected to the turning forces created during the sport of alpine skiing. The technological advancements defined by the invention minimize the amount or extent to which a ski's edge angle deteriorates or degrades along the ski length when subjected to extreme loading created by high performance skiing.